1. Field of the Invention
The present invention relates to a resist composition, a method of forming a resist pattern using the resist composition, a compound useful as an acid generator for a resist composition, and an acid generator.
2. Description of Related Art
In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure to radial rays such as light or electron beams through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.
For miniaturization of semiconductor devices, shortening of the wavelength of the exposure light source, and increasing of the numerical aperture (NA) of the projector lens have progressed. Currently, exposure apparatuses in which an ArF excimer laser having a wavelength of 193 nm is used as an exposure light source and having a NA=0.84 have been developed. As shortening the wavelength of the exposure light source progresses, it is required to improve various lithography properties of the resist material, such as the sensitivity to the exposure light source and a resolution capable of reproducing patterns of minute dimensions. As a resist material which satisfies these conditions, a chemically amplified resist is used, which includes a base resin that exhibits a changed solubility in an alkali developing solution under action of acid and an acid generator that generates acid upon exposure (Patent Document 1).
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are now typically used as base resins for resists that use ArF excimer laser lithography, as they exhibit excellent transparency in the vicinity of 193 nm.
Here, the term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position. The term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and a methacrylate having a methyl group bonded to the α-position.    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2003-167347